INFLUENCE OF VARIOUS FACTORS. 567 
which has to deal with nitrogen in excess of the requirements of the 
body. 
After every kind of food the absorption of bile salts and their action 
on the liver must be taken into account as a factor in increasing the 
flow of bile (see p. 563). 
Influence of pressure of surrounding structures. — The liver, 
being situated just below the diaphragm and above the abdominal 
viscera, is subject to marked variations in pressure. It has already 
been pointed out that a considerable quantity of bile may colled in 
the bile passages. By pressure from adjacent organs, this may be 
squeezed out, The facts that section of one vagus reduces the bile flow 
only when the frequency of respiration is diminished, 1 and that section 
of the vagus just above the diaphragm, which has no influence on the 
rate of respiration, leaves the bile secretion unaltered, and that stimula- 
tion has also no effect, seem to indicate that the flow of bile is acceler- 
ated by respiratory movements. 
The very marked rise in the amount of bile poured out between four 
and eight a.m. in a case of biliary fistula, 2 just at the time when the 
patient wakened and commenced to move about, further supports the 
view that pressure on the liver may cause an increased flow of bile. 
Direct influence of nerves upon bile secretion. — It has already 
been pointed out that the secretion of bile may 1 >e indirectly modified 
by the influence of nerves upon the blood vessels. The flow of bile may 
also be increased through the stimulation of the nerves to the muscular 
coat of the bile , ducts and gall bladder. Keflex stimulation through 
these nerves probably accounts for the first gush of bile after food is 
taken. There is, however, no evidence that stimulation of nerves can 
directly increase or diminish the actual secretion of 1 die — any change 
in the flow being fully explained by indirect action. The facts that 
the injection of pilocarpine, which so markedly increases the flow of 
saliva and of pancreatic juice, has no influence on bile secretion, 3 and 
that atropine has no action in arresting the secretion, 4 seem to oppose 
the idea that there is any direct nervous influence upon the process. 
Influence of various chemical substances on bile secretion. — 
Certain substances, when introduced into the portal Hood, either directly 
or through the alimentary canal, cause an increase in the secretion of bile. 
Tarehanoff 5 found that when haemoglobin is injected into the blood- 
vessels the bilirubin of the bile is increased in amount. Stadelman 6 and 
Afanassiew 7 afterwards demonstrated that such drugs as toluylenediamin 
and arseniuretted hydrogen, which cause the solution of haemoglobin 
from the blood corpuscles, produce not only an increase in the bilirubin 
of bile, but also an increased flow of bile, and that this polycholia seems 
to be proportionate to the destruction of haemoglobin. It is therefore 
clear that the passage of free haemoglobin to the liver acts as a stimulant, 
and may produce an increased flow of bile ; and hence all substances 
which bring about an escape of the blood colouring-matter tend to 
increase the secretion of bile. 
1 Hermann's " Handbuch," S. 270. 
- Rep. Lab. Roy. Coll. Fhys. , Edinburgh, vol. iii. p. 200. 
3 PaschMs, Med. Jahrb., Wien, 1884, S. 169. 
* Paitherford, "Action of Drugs on the Secretion of Bile," Edinburgh, 1880, p. 96. 
5 Arch. f. d. ges. Physiol., Bonn, 1874, Bd. ix. 
8 Arch. f. exrper. Path. u. Pharmakol., Leipzig, 1883, Bd. xcviii. S. 460. 
7 VirchoiosArchiv, 1884, Bd. xcviii. S. 460. 
